Finance Receivables by Credit Quality Indicator and Portfolio Class (Detail) (Financial Services, USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	$ 8,877.2	$ 8,820.1
Pass
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	8,761.6	8,713.0
Special Mention
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	40.1	56.5
Substandard
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	75.5	50.6
Dealer | Wholesale
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,643.0	1,616.5
Dealer | Wholesale | Pass
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,611.0	1,576.9
Dealer | Wholesale | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	16.0	31.1
Dealer | Wholesale | Substandard
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	16.0	8.5
Dealer | Retail
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,512.8	1,525.6
Dealer | Retail | Pass
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,511.3	1,520.1
Dealer | Retail | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1.5	5.5
Customer Retail | Fleet
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	4,543.4	4,442.5
Customer Retail | Fleet | Pass
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	4,480.4	4,396.5
Customer Retail | Fleet | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	14.4	12.7
Customer Retail | Fleet | Substandard
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	48.6	33.3
Customer Retail | Owner/Operator
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,178.0	1,235.5
Customer Retail | Owner/Operator | Pass
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	1,158.9	1,219.5
Customer Retail | Owner/Operator | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	8.2	7.2
Customer Retail | Owner/Operator | Substandard
Financing Receivable, Recorded Investment [Line Items]
Financing Receivables	$ 10.9	$ 8.8